Split sys_getpeername() and sys_getsockname() so they can be called when the
'name' is wanted in kernel code.
Similarly split sys_accept() and change the split in recvmsg() so that it
is useful to the compat functions, recvit() is removed and replaced by
do_sys_recvmsg().
Factor out the code that writes socked names to userspace (from mbuf) to
avoid replicated code.
Extract the code that writes socket 'control' (CMSG) data out to userspace,
being more careful about the 'fd' that may exist inside SCM_RIGHTS msgs.
(they still get lost if some of the latter copyout calls fail).
Since these are new functions, and old LKMs will fail to load.